Machine control



c. F. FRYE MACHINE CONTROL 3H3 n" 1 .1 h.

Sept. 22, 1953 '7 Sheets-Sheet 2 Filed Dec. 16, 1946 Sept. 22, 1953 c,F. FRYE MACHINE CONTROL 7 Sheets-Sheet 3 Filed Dec. 16, 1946 Sept. 22,1953 c. E. FRYE 2,652,732

MACHINE CONTROL Filed Dec. 16, 1946 7 Sheets-Sheet 4 C. F. FRYE MACHINECONTROL.

Sgpt. 22, 1953 '7 Sheets-Sheet 5 Filed Dec. 16, 1946 fizkefziox' Carlegs' F/Fr'ye Sept. 22, 1953 C. F. FRYE MACHINE CONTROL 7 Sheets-Sheet6 Filed Dec. 16, 1946 hazzr 67227125 2 e Sept. 22, 1953 c. F. FRYEMACHINE CONTROL 7 Sheets-Sheet '7 Filed Dec. 16-, 1946 9.9 I DOW/VTHRUSTw l M surf/25b CONTACT' Patented Sept. 22, 1953 UNITED STATES PATENTOFFICE MACHINE CONTROL Charles F. Frye, Chicago, Ill.

Application December 16, 1946, Serial No. 716,543

Claims.

My invention relates to automatic controls for machinery and includesamong its objects and advantages a simple type of equipment of greatversatility in adaptation to a wide variety of linear motions incomplicated operations; and a controllable degree of sensitivity toload, whereby many mechanical operations not otherwise susceptible toautomatic control can be achieved under such control.

The use of automatic feeds in drilling, and to an only slightly lesserextent in other operations, such as planing, milling and turning, issubject to the objection that an automatic feed with a positive powerdrive, is not sensitive to the force required to produce the feed. Ofcourse, it is possible to make the drive for the feed of sufficientstrength and power so that the work gets done, but this compels thecutting tool to move at a constant rate of feed during certain criticalperiods when constant feed is undesirable. On this account a common typeof multiple spindle drill has each spindle arranged for hand feed, witha clutch which the operator can throw in to give power feed after theoperator has started the drill into the work. This makes it necessaryfor the operator to start the drilling operation by hand and then throwthe clutch to shift over to power feed, but it does enable the operatorto nurse the drill through the surface, or skin of relatively hardmetal, by limiting the force applied and permitting the drill tohesitate a little as it works into cutting position in the body of themetal. Forcing the drill to feed at constant rate at this time resultsin excessive wear on the cutting edge of the drill and limits theapplicability of automatic feeds.

Similarly, when it is desired. to drill a blind hole to a predetermineddepth, an automatic trip that throws out a feed operating at constantspeed cannot be operated reliably to get a constant depth and the depthof successive holes will vary by several thousandths of an inch. Withthe force-sensitive timed feed according to the invention, it ispossible for an inexperienced operator to drill blind holes, and theautomatic features of the control will give holes of exactly identicaldepth with an accuracy down to precision tolerances.

With respect to these, and. other practical matters involving the manualskill of an expert mechanic, equipment according to the invention iscapable of a close approximation to the sensitivity of the human hand.This permits many laborious tasks hitherto considered possible only byhand operation to be performed on an automatic or semi-automatic basis.

In th accompanying drawings- Figure 1 is a side elevation of a drillpress equipped with a simple form of control according to the invention;

Figure 2 is an enlarged elevation of the singlepressure control box ofFigure 1 with the cover removed;

Figure 3 is a section on line 3-3 of Figure 2 showing the constructionof the solenoid valve;

Figure 4 is a plan view of the valve block of Figure 2;

Figure 5 is a section on line 5--5 of Figure 4;

Figure 6 is a section of the quick release valve of Figure 1;

Figure 7 is a section on line l-1 of Figure 6;

Figure 8 is an enlarged section of the valve seat on line t-s of Figure4, which is the same plane as line 5-5;

Figure 9 is a view similar to Figure 2 showing a double-pressure controlbox;

Figure 10 is a section through the difi'erential relief valve of Figure9;

Figure 11 is a side elevation of a mechanical reset timing switch;

Figure 12 is an end view of the switch of Figure 11;

Figure 13 is a diagram indicating the application of two control boxesto a timed sequence operation for a plurality of otherwise independentmechanisms;

Figure 14 is a wiring diagram for the simple manual control of Figure 1;

Figure 15 is a wiring diagram for timed deephole drilling;

Figure 16 illustrates the readjustment of the wiring of Figure 15 tosecure repeated operation without timing;

Figure 17 is a wiring diagram for controls in which full power isavailable for moving the parts in both directions;

Figure 18 is a wiring diagram employing a single pole switch;

Figure 19 is a force diagram for ordinary drilling; and

Figure 20 indicates an automatic disconnecting shunt.

Simple direct feed In the embodiment of the invention more particularlyillustrated in Figures 1 and 2, I have indicated one of the simplestforms of equipment according to the invention. The conventional drillpress includes the standard Ill, work table l power head !2, and spindleI3, which may be reciprocated vertically by rotating the cross shaft 14provided with three equally spaced radial handles it for the convenienceof the operator.

This also activates the pivoted sector i6 meshing with the same pinionon shaft is which engages the teeth of the rack I! to move the spindlel3. The sector IB also carries a crank arm l8 connected by means of anadjustable pitman iBa extending down through a conventional packing I 8bto connect with the piston iii in the cylinder 20. The cylinder may besuitably supported in any desired position as by means of a bracket 2|.The pitman [8a carries an abutment 22 receiving the thrust of thecompression spring lab to hold the parts in the position shown in thedrawings.

Air under pressure may be introduced into the cylinder 2b to force thepiston [9 down and actuate the spindle is. As best indicated in Figure 6the connection and relief fitting 24 comprises a hexagonal body having apipe-threaded connection at E to a source of air pressure and aconnection at to the cylinder 29. The connection 25 is in communicationwith a lower passage 21! and the connection 25 with an upper passage Twomeans of intercomrnunication are provided between the passages 27 and28. The check valve ball when there is no pressure in passage 2?, li sat rest on the supporting plug 3% and is guided from its position ofrest to the position illustrated in Figure 6 by a guide made of a coilspring 3|. When pressure is suddenly delivered through the passage 21,the flow of air upward into passage 28 lifts the ball 29 into firmengagement with its seat as indicated in Figure 6. Thereafter air underpressure can only find its way to passage 23 through the othercommunication.

The second communication comprises the passage 32, adjustably throttledby the threaded cone-valve member 33, which may be clamped in adjustedposition by a lock nut 36.

It will be apparent that when pressure is delivered to passage 21 as bymeans of the pipe 35, there will be a slight free discharge into passage28 until the ball 29 has found its seat, after which the rate ofdelivery of power to the piston it will be at a slower, substantiallyconstant rate, corresponding to the desired rate of feed for the machinetool controlled. However, because the force on the spindle depends onthe air pressure in the cylinder whenever the drill strikes a hard spotit can and does slow down or hesitate in its progress. Thus the pistonand cylinder effect a resilient lost-motion connection between the powersource and the feed mechanism for advancing the tool. By automaticallylimiting the maximum pressure available in the supply pipe 35, to avalue corresponding to a feeding force that the drill can stand withoutinjury, it is possible to have automatic feed without breakages andwithout requiring the operator to nurse the drill point into the workbefore the feed is made automatic.

Simple return stroke It will be apparent that when the pressure supplyin pipe fails, as by connecting that pipe to atmosphere, the contents ofthe cylinder til can escape at a very rapid rate, finding its exitthrough passage 2?.) and down around the ball 29 with extreme freedom,so that the spring iilb can return the parts to the position shown inFigure 1.

Simple control panel In Figures 2 to 5, inclusive, I have indicated thesignificant details of a simple standard control panel, illustrated at36 in Figure 1 as con nected by a pipe 31 to a source of air pressure38.

Referring to Figure 2, the casing 39 houses a stepdown transformer 49 towhich a 120 volt alternating current may be delivered subject to thecontrol. of a manual master switch 42 (see Figure 1).

Air under pressure is received through the connector 44 and conveyed toa conventional pressure reducing valve 46, the adjusting handle 41 ofwhich projects through the cover of the housing 39 to be accessible tothe operator. From the pressure reducing valve the air at reducedpressure enters the control block $8 at the inlet 49. The gauge 4-5 isprovided for the convenience of the operator in knowing what pressure heis getting. From the inlet iii the air may find its way to thehorizontal passage 55 subject to control by a first solenoid valve s2.The passageway always connects at 54 to the actuating cylinder and tothe chamber 5% controlled by the right solenoid valve 57. It will beapparent that with the left solenoid valve 52 open and the right closed,operating pressure will be delivered to the cylinder subject to thethrottle valve 32. But if the relationship is reversed, the passageway50 no lon er receives air under pressure, being cut on" from the inlet53, and functions as a discharge passage through the chamber 55 andexhaust opening 58. The insulating panel it carries a fuse lil andterminals 86 for the low voltage wiring connections.

The solenoid valve Each of the valves 52 and 51 includes a rubber seat58, which may be assembled in the holder to by pushing it downmechanically through the discharge opening 52 until it seats below thedownwardly facing shoulder, 86. The holder may be threaded into theblock 48, and is notched at to improve the cross sectional area of theopening available when the cone valve 151 is lifted. Each cone valvemember is non-magnetic and comprises a conventional head and a. shank 68provided with an enlargement 69 at its upper end. The magnetic hammerelement ii! has lost motion connection by reason of sliding movement onthe shank 68. The hammer it is guided in the tube 12 which is brazedinto the supporting nut 14. The winding T6 is preferably enclosed in ahousing ll. It will be apparent that when the winding is energized, thehammer ill will rise rapidly and acquire considerable speed before ithits the shoulder 63 so that the valve head will be liftedinstantaneously. The downward movement will also acquire a fair amountof speed before the valve closes, but this is less important because thepressure difference at the time the valve closes is very small. Thecombination of the rubber seat and the extremely quick opening reduceserosion by air flow at the point of closure to a minimum and secures aconstruction of very long service life.

Double pressure control Referring now to Figures 9 and 10, it ispossible to secure greater flexibility in cushioning and return movementby employing pneumatic pressure on both ends of the actuating piston.{he box 82 may house the identical pressure reducing valve 48 anddistributing block it and solenoids 52 and 57 illustrated in Figure 2,as well as the step-down transformer at. In place of the spring I81) Iprovide a second independent pressure-reducing valve 84 discharging tothe control block 86 with an additional pressure gauge ii! connected toshow the pressure in the cylinder 88 below check valve 89 into thepassage 90, which communicates with the pipe 92 leading to the lower endof the cylinder 88. Communication between the passage 90 and atmosphereis controlled by two valves arranged in series. The first valve 94 is aduplicate of the solenoid control valves 52 and 51 but the lower end ofthe holder 60 forms a seat for a spring-held relief valve 96 adjustablytensioned against its seat by the adjusting nut 91 provided with airvent 98. With the valve 94 open, the pressure on top of the piston canmove the piston down and the contents of the cylinder below the pistoncan escape through the valve 96, which is set to operate at a pressureslightly higher than that delivered by the reducing valve 84. Thereforethe valve 94 is held up by ener gizing its solenoid during the workingoperation. But where the resistance to the feeding movement decreasesrapidly as the machining operation nears a close (as in the case ofdrilling a hole or milling a slot) the force applied to the feed can bereduced at the critical point by letting the valve 94 fall shut as thetool begins to break out of the work.

This makes it possible to secure operation substantially according toFigure 19 in which the dotted line 99 indicates the effective downthrust on the top of the piston and the dash line I00 indicates theeffective resistance of the air below the piston. Upon reference toFigure 19 it will be noted that at the initial contact between the tooland work, the force on top of the piston is not appreciably greater thanthat below it, but the contact between the tool and the work resists thefeeding movement and permits the throttle 32 to let the pressure buildup gradually as the tool enters the work, to a maximum which will bemaintained until the work is finished. It will also be noted that thedash line I00 will begin to curve upward sharply at the point indicatedas "relief cutout" on the drawing and the resistance of the air belowthe piston will increase at an increasingly rapid rate thereafter. Thuswhen the tool begins to break out of the work the effective force on thepiston has already been reduced a little and by the time it finishesbreaking out of the work, the force may be reduced to a very minorfraction of its maximum value. In fact, after the tool has moved a shortdistance beyond the finishing position, the cushioning action equals thedown thrust at I02 and there will be no tendency for the tool to lurchforward violently to the limit of its movement.

Suitable electric contacts may be positioned along the path of movementof the tool to enable the operator to adjust the operation to suit thework. Thus in Figure 1 I have diagrammatically indicated an extensionI04 on the spindle I 3, provided with a bridge I06 on one side adaptedto operate a switch I01 for controlling the value 94. The length of thebridge determines the distance through which the valve 94 will be heldopen and the switch may be mounted for vertical adjustment on a slideI08 to secure precise timing of the relief cutout point shown in Figure19, The other side of the extension may carry a projection I 09 tocontact a switch H0 at the top of the path of movement and conditionsolenoids 52 and 51 for the down stroke, and to contact a switch I I2 tocondition the same solenoids for the return stroke at substantially thepoint I02 of Figure 19. Switches H0 and H2 may be adjustly mounted on asingle slide H4.

Timed dwell Referring now to Figures 11 and 12 I have indicated amicroswitch I I6 housed in a suitable channel-shaped support I I! andoperated to open and close a circuit by pressure on the finger I I8. Toactuate the finger I provide a timing mechanism involving an oil filleddash-pot I I9 having a working space I and an enlarged bore I22 abovethe working space. The plunger I24 is a loose fit in the working space I20 and is provided with a vent passage including a check valve I26 whichpermits liquid to fiow into the working chamber but not out of it. Theupper end of the plunger carries a bracket I21 having a projection I23overlying the end of the finger II8 to depress the same. The plunger andbracket are held up in the position of Figure 11 by a compression springI29. The push rod I30 telescopes freely in the plunger I24 and carriesan abutment for the upper end of the compression spring I32, the lowerend of which bears on the upper end of the plunger I 24.

It will be apparent that if the push rod I30 is forced down, theincreased tension of the spring I32 will result in an unbalanced forceto move the plunger I24 down, but this movement will be damped by theliquid in the working space, which has to leak up around the sides ofthe plunger. Thus it is easy to design the parts so that a period offrom two to as much as fifteen seconds elapses before the projection I28has moved down to the limit of its movement. By pivoting the microswitchat I34 and adjusting its position with the adjusting screw I36 theposition of the finger I I8 may be shifted to secure any desired delaywithin the capacity of the device.

Means are provided for depressing the plunger I30 when the tool comes tothe end of its desired path of movement. I have indicated a ball contactI31 at the upper end of the push rod we and a rocking lever I38 pivotedat I39. The rocking lever may be positioned where a suitable projectionfrom a spindle or tool carriage will engage it, and is of sufficientmechanical strength to hold the spindle against movement under the forceof the actuating piston. I have indicated a heel I40 to limit themovement of the lever I38 in the other direction. By extending the heelI 40 at I 4| convenient mechanical contact is provided for machineelements moving in either direction.

When it is desired to feed any tool, such as a drill, end broach ormilling cutter, so that it will cut into the work up to a predeterminedpoint with a high degree of precision, the equipment of Figures 11 and12 may be employed in such a way that the tool carriage moves with ahigh degree of precision to a predetermined position and remains in thatpredetermined position for a predetermined time, which may amount toseveral seconds, while the cutting tool continues to turn against thework and load distortions of the frame of the machine are relieved. Thenwhen the microswitch is closed and the tool backs away it will be foundthat the bottom of the hole or the end of the out has been finished withprecision. With such equipment it is not difficult to drill blind holesautomatically and have all the holes of the same depth within one-halfof one thousandth of an inch, and with a little greater degree of caresomewhat higher precision is obtainable.

It will be apparent that because the feeding instrumentality isforce-sensitive and hesitates momentarily and only exerts apredetermined maximum feeding force, no harm is done if the tool carrieris arrested with a fixed stop at any time, either to discontinue thetooling or to postpone it while some other operation is taking place.

Unit correlation In Figure 13 I have indicated a combination of twocontrol boxes I42 and I44 to correlate and synchronize the operation ofa plunger I46 for forcing a blank through a die M8 to deliver a formedbox I50, and a slide IE2 for feeding a blank from a pile I54 intoposition to be operated on by the plunger N36. The plunger is actuatedby the piston I55 and the slide by the piston I56. The plunger carriesan extension I58 with a contact arm 66 to engage the control switch I62at the top of the stroke and the control switch IE4 at the bottom of itsstroke. Similarly, the slide carries an extension I65 to actuate aswitch iBB at the forward end of its stroke and the switch I at therear. Subject to the delivery of energy to the master switch I12, theplunger I46, at the bottom of its stroke completes a circuit in thecontrol box I44 to start the plunger I56 forward. But the initialforward movement operates the switch I'JEI to lift the plunger I46 sothat it will be out of the way before the slide IiiZ begins to move anew blank into position. And as soon as the slide I52 has the new blankin position it operates the switch I68 to start the plunger its down.But the initial movement of plunger I55 operates the switch I62 to startthe slide I52 back to its initial position, where it will remain untilthe plunger I46 finishes its work and again actuates. the switch I64 tostart a new cycle. Thus the full equivalent of a completely automaticspecial-purpose machine can be secured by aciding simple stock controlsto old machines heretofore operated by hand or by cams, with or withoutstorage of partly finished parts between successive operations. Alsoreadjustments to change the size operated onor even the sequence ofoperations may be made on the spot without redesigning complicatedautomatic transmissions.

Wiring for single direction manual controlled operation Referring toFigure 14, the step down transformer 40 may receive full line voltagefrom the power lines Ila subject to the control of a master switch H6. Iprefer to reduce the voltage to a point where insulation for wiring thatmay come in contact with metallic machine parts need not be ofabnormally high durability or breakdown resistance and where thetendency to arc on the switch contacts is greatly reduced. I have foundthat with the voltage as high as 24 volts ordinary switches can operateto make and break a circuit 15,000,000 times or so withoutdeterioration, and that a short circuit will blow a simple fuse withoutinjuring anything. Also, such a voltage is harmless if the operatorshould happen to expose himself to it.

The low voltage side of the transformer delivers current to lines I18and I80, one of which includes the safety fuse I9. I connect a signallight I82 past the fuse I9 and across a minor fraction of the lowvoltage winding so that the light will burn low as long as the fuse isin good condition. When the fuse is out the lamp burns more brightly butdoes not pass enough current to maintain an are or to operate the powerelements beyond. But the operator can hunt for a short circuit bymanipulating the parts, and when he finds it the light will tell him.

For simple manual control I provide a control switch I 83 which deliverscurrent in one position to the power solenoid 52 so that its valve willbe open while the exhaust solenoid 51 remains inactive. When theoperator moves the switch I83 back to the position of Figure 14 thepower solenoid is no longer energized and its valve closes while theexhaust solenoid'connects the pipe 35 to the atmosphere and the toolreturns to initial position. To add the automatic cushioning actiondescribed in connection with Figure 19 it is only necessary to use thecontrol box of Figure 9 and wire the solenoid I84 for the valve 94through a contact switch I86 closed by the tool carriage at the properpoint.

Deep hole drilling Referring now to Figure 15 I have indicated a slowlyrotating 6E8 adapted to oscillate a switch iilii into either of twopositions. I provide an additional solenoid lei adapted to move a doublethrow switch, including contacts I94 and I96 from the position indicatedin Figure 15 to the right against the other set of stationary contacts.To start the operation the operator momentarily closes a push buttonswitch I98 establishing a circuit through conductor 200, switch 202,conductor 2% to the contact I96 and conductor to the solenoid I92 andthrough the solenoid to the return line i853. This moves the contactssec i953 to the right.

Movement of the contact I96 to the right completes a holding circuit forthe solenoid I92 as follows: from line ill; through switches 268 and 2H!and conductor M2 to the stationary contact 2M. From and through contactIts and con ductors tilt and tilt through the winding I92 to the otherline Iitl. Movement of switch I to the right also completes a circuitthrough the power solenoid 5'5 follows: from line {16 through conductorMt to the finger I90 then through conductor did to the contact I94; thenthrough stationary contact through conductcr 222, solenoid iii andconductor 224 to the cross connection 226 and'to the other line I80.Subsequent return of the finger IE!) to the position of Figure 15 willbreak this power circuit and establish the exhaust circuit as follows:from line I16 through switch tIS, conductor ZIG, finger I98 andconductors 223 and through the exhaust solenoid 52 and conductor 232 tothe cross connection 225 and the line see. Thus, as long as the operatordoes not do anything to change the sequence of operations, the drillwill be applied with the desired predetermined force for a predeterminedtime and then lifted out of the hole to clear pieces and cool itself fora different predetermined time and this sequence of operations willcontinue indefinitely until the hole is drilled.

The sequence of operations which is described may advantageously besupplemented, if desired, by providing a cushioning solenoid Hi lcontrolled by a contact switch itifii which will be operated, in case ofa through hole, when the drill finally works its way through after anindeterminate number of successive undulations.

Single cy is To change the wiring to a single cycle operation, theswitch 225 and its mechanically connected companion switch are shiftedto the right. This renders the automatic timing device I88 inoperativeand operation thereafter is as follows:

Normal momentary closure of the foot switch I98 completes the sameinitial circuit for solenoid I92 as in Figure 15. But the holdingcircuit is from line I'I6 through switches 208 and 2E9, conductor 2I2,contact 2M and conductor 2% and 206 through the winding I92 to line I80.Movement of contact I94 to the right completes the power circuit asfollows: line I16, switch 2I5, line 2I8, contacts I94 and 220 throughsolenoid 57 to line I80. The tool now moves down through its entireworking stroke. When it reaches the bottom, mechanical contact opens theswitch 266, which opens the holding circuit through solenoid I92 andcontacts I94 and I96 go back to the left again with power solenoid 57deprived of power and contact I94 delivering to the exhaust winding 52.This brings the spindle back up and at the top of the stroke the spindlecomes to rest and nothing more will happen until the operator startsanother cycle.

Automatic nepeated cycle To change to automatic repeated cycleoperation, switch 202 is moved up and switch 208 is moved down. Then itis necessary for the operator to keep his foot continuously on switchI98 to secure continuous automatic cycle operation. The initial start isby closing switch 280 momentarily, which completes a circuit as follows:from line I16 through switches I98, 268, Zlll, conductor 2 I2, switch240, switch 202, conductors 204 and 286 and winding I92 to line I80.Thereupon contacts I94 and I96 move to the right and contact I96completes a holding circuit as follows: line H6, switches I98, 208, 2I0,conductor 2E2, contacts 2I4 and I96, conductors 204 and 266, throughwinding I92 to line I80. The power solenoid 5 is supplied with power bycontact I94 as in single cycle operation until the bottom of the strokeis reached when switch 2I0 is mechanically opened and solenoid I92 isde-energized and the contacts move back to the position of Figure 16 andthe spindle comes up again. At the top of the stroke switch 240 ismomentarily closed by the spindle and solenoid I92 again receives energyand coinpletes its own holding circuit and a complete cycle takes placeover and over again as long as the operator keeps his foot on switchI98.

In both the single cycle and automatic repeated cycle operations the endof the down stroke may be cushioned as before by means of solenoid I84and position switch I86.

Straight operator control By a simple change of one switch from thesingle cycle adjustment the same wiring can function without anyautomatic action as follows: switch 208 is moved to neutral position.Now closure of switch I98 by the operator at the machine completes acircuit through solenoid I92 as follows: from line I I6 through switchI98, conductor 242, switch 202,'conductors 204 and 206, winding I92 toline I80. This moves the contacts to the right and the power solenoid isenergized and the exhaust solenoid tie-energized and the tool goes towork. When the operator opens switch I98 the circuit through solenoidI92 is broken and the parts go back to the position of Figure 16 and thetool goes back up.

Power return Referring now to Figure 17 any one of the arrangements ofFigures and 16 previously discussed may be adapted for power return ofthe tool by merely using two sets of solenoids 52 and 51 with theirvalve block 48, and connecting the the place of the spring 23.

second set to the bottom of the cylinder 28 to take In Figure 1'? I haveindicated the commonest arrangement for operation in this way, omittingnon-essential portions of Figures 15 and 16. Closure of the foot switchI98 establishes a circuit from line 1736 through switches I98 and 2 illand at the top of the stroke switch 240 is momentarily closedmechanically, which delivers current to the winding i92 and line I80.Contacts I94 and I96 move to the right for the down stroke and at theend of the down stroke the mechanical opening of the switch 2 it willlet the parts move back to the position of Figure 17 until the return ofthe tool to the top of the stroke momentarily closes switch 240 againand starts the next cycle. To deliver power to both ends of the cylinderit is only necessary to add the exhaust solenoid 244 for the bottom ofthe cylinder, connected in parallel with the power solenoid 51, and thepower solenoid 226 for the bottom of the cylinder, connected in parallelwith the exhaust solenoid 52 for the top of the cylinder. The cushioningby means of solenoid I84 and switch I86 functions just as before.

Single pole automatic Where less adaptability to operate in a pluralityof different ways is required, the simplified wiring of Figure 18 willsecure automatic repeated cycle operation as easily as the more completewiring. Referring to Figure 18, closure of foot switch I88 at a timewhen the tool is at the top and switch 248- is momentarily closed, willcomplete a circuit from line I16 through switches I98 and 240 and lineI80, which moves the single contact 248 to the right and completes aholding circuit through line I16, conductor 258, contacts 248 and 252,switch 2I0 and winding I92 to line I80. The power solenoid 57 is nowenergized and the exhaust solenoid 52 de-energized and the tool movesdown. At the end of the feed stroke switch 2I0 is momentarily opened,which deenergizes solenoid I92 and the parts move back to the positionof I92 with the power solenoid deenergized and the exhaust solenoidenergized and the tool comes back up. Cushioning solenoid I84 andposition switch I86 function as before.

In Figure 20 I have indicated a chamber 254 containing a pressuresensitive diaphragm 256. The chamber is connected in shunt around thethrottle 32 with the pressure on the high pressure side of the throttlecoming in on top of the diaphragm 256 and the pressure on the lowpressure side of the throttle below the diaphragm. The diaphragm may bebiased by compression spring 258, which may be adjusted by the set screw260. I have indicated conventional circuit-closing connections in thenature of a two-conductor cable 262 connected through the insulatingbushing 264 to contacts 266 and 268, with an adjustable contact screw210 carrying an insulating button 212 overlying the contact 268. It willbe apparent that the adjustment screws 260 and 270 can be adjusted sothat the diaphragm will complete a circuit at a predetermined pressuredifference across the throttle 32. By adjusting the parts so that thiscircuit is closed when pressure becomes practically zero, it is possibleto arrange any of these automatic controls so that if anything happensto stop the feed of the tool, a few seconds after the feed stops thepressure across throttle 32 is equalized and the whole machine is shutdown until the operator comes to remedy the difliculty.

It will be apparent that any numberof otherwise independent mechanismscan be correlated in any sequence of operations and that by the conjointuse of the slow and gentle action of the throttle-fed pneumatic pistonand the timed delay in the closure of any circuit by means of theequipment of Figures 11 and 12, any sequence of operations can be madeautomatic on such a basis that if any of the individual operations isinterrupted or delayed, the succeeding operations will wait for itautomatically. Thus, in the use of a continuous kiln or leer we mighthave a following sequence of operations:

(1) Open the inlet door; (2) insert the material; (3) close the inletdoor; (4) turn on steam; (5) turn off and exhaust steam; (6) open anoutlet door; (7) remove-the material through the outlet door; (8) closethe outlet door; (1) open the inlet door at the beginning of the nextcycle. It will also be obvious that the gentle pneumatic operation wouldbe equal- 1y advantageous in case such a series of operations were to betimed by means of a number of cams on a rotating shaft, but in that casefailure of one step might result in premature performance of the nextstep, with attendant damage.

For instance, in feeding work pieces on a rotary carrier member to andfrom a machining tool, the interruption of the movement of the rotarymember with high precision in each successive position is a verydifficult mechanical problem. According to this invention, such a rotarymember can be replaced by a simple slide that moves to and fro betweenfixed stops which, because they are permanently stationary, can functionwith high precision. The slide moves to one end of its path and while amachine operation is performed on one end of the slide the other endprojects for removal of the finished piece and reloading by the operatorand then the slide moves to the other end of its path, and so onindefinitely.

Others may readily adapt the invention for use under various conditionsof service by employing one or more of the novel features involved, orequivalents thereof. A at present advised with respect to the apparentscope oi my invention I desire to claim the following subject matter.

I claim:

1. In a pneumatic machine control, in combination: a pneumatic cylinder;connections between said cylinder and the feed mechanism of a machinetool for actuating said ieed :mecha nism; said cylinder having an inlet;a fitting adjacent said inlet; two passages through said fittingcommunicating with said cylinder; one of said passages includingadjustable throttling means continuously operative; the other of saidpassages containing a check valve preventing flow into said cylinder;said check valve being normally open and adapted to admit apredetermined small quantity of fluid quickly before the infiowing fluidcloses said valve; a supply conduit communicating with both passages;and means for connecting said supply conduit to atmosphere or to asource of fluid under pressure.

2. In a pneumatic machine control, in combination: a pneumatic cylinder;connections between said cylinder and the feed mechanism of a machinetool for actuating said feed mechanism; two passages to said cylinder,one of said passages including adjustable throttling means continuouslyoperative; the other of said passages containing a check valvepreventing flow into said cylinder; said check valve being normally openand adapted to admit a predetermined small quantity of fiuid before theinflowing fluid closes said valve; a supply conduit communicating withboth passages; and valve means for connecting said supply conduit toatmosphere or to a source of fluid under pressure.

3. In a pneumatic machine control, in combination: a pneumatic cylinder;connections between said cylinder and the feed mechanism of a machinetool for actuating said feed mechanism; two passages to said cylinder,one of said passages including adjustable throttling means continuouslyoperative; the other of said passages containing a check valvepreventing the flow into said cylinder; said check valve being normallyopen and adapted to admit a predeter mined small quantity of fluid athigh velocity before the inflowing fluid closes said valve; a supplyconduit communicating with both passages; valve means for connectingsaid supply conduit to atmosphere or to a source of fluid under apredetermined pressure; and means for adjusting said predeterminedpressure to various values.

4. In a pneumatic control system for machine tools, in combination: afitting having a through passage; a first check valve in said passagepermitting flow in one direction only; a lateral passage communicatingwith said through passage and with atmosphere; an externally controlledvalve in said lateral passage adapted to open and close said lateralpassage; and a spring-held adjustable check valve in said lateralpassage between said externally controlled valve and atmosphere,constructed and arranged to prevent fiow into said passage but to permitflow out of said passage at pressures above a predetermined pressure.

5. In a pneumatic control system for machine tools in combination: afitting having a through passage; a pressure source connected to one endof said passage; a check valve in said passage permitting flow away fromsaid source only; a lateral passage communicating with said throughpassage beyond said check valve, and with atmosphere; a control valve insaid lateral passage adapted to open and close said lateral passage; anda spring-held adjustable check valve in said lateral passage betweensaid control valve and atmosphere, constructed and arranged to preventflow into said passage but to permit flow out of said passage atpressures above a predetermined pressure only.

CHARLES F. FRYE'.

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